2-8% of cases of acute myelogenous leukemia have associated myeloid sarcoma.
Also known as chroma, due to its green appearance from myeloperoxidase enzyme in myeloblasts.
Most cases of myeloid sarcoma progress to AML.
Male:female 1.2:1.0.
Median age 56 years.
Immunophenotyping CD68-KP1 is most commonly expressed marker.
Positive markers include myeloperoxidase, CD117, CD99, CD68/PG-M1, Lysozyme, CD34, terminal deoxynucleotidyl transferase, CD56, CD61/linker of activated T lymphocyte/vW antigen, CD30, glycoprotein A and CD4.
Its presence associated with AML even in the absence of peripheral or bone marrow blasts.
Accumulation of extramedullary, ectopic acute leukemic cells.
More often associated with monocytic leukemia, and with t(8:21) translocations or rearrangements of 11q23.
Most common sites of accumulation of myeloid leukemias are bone, lymph nodes, periosteum, soft tissues and skin.
Can manifest AML months to years later.
At autopsy 11-36% of AML have ovarian involvement and 11% have uterine involvement (Barcose M et al).
Rarely leukemia does not develop.
Can occur in known AML in active disease or as manifestation of relapse.
May occur in blastic transformation of CML, chronic myeloproliferative disorder, or myelodysplastic syndrome.
Treatment is the same as AML and systemic therapy should be given to all patients.
Surgical removal of the lesion and/or radiation is indicated for bulky disease or if spinal cord involvement is present.
Many patients are misdiagnosed as having an aggressive lymphoma.
Most patients should be treated with AML like intensive chemotherapy, which is associated with prolonged overall survival and failure free survival generally occurs only when high-dose therapy is followed by stem cell transplantation.